The invention relates to a method and a apparatus for structuring components using a material based on silicon oxide, in particular silicate glass, glass ceramic, or quartz.
Silicon and glass wafers are among the materials used most frequently in microtechnology. Glass is increasingly gaining in significance for various MEMS applications (micro-electromechanical systems). In addition to the classical use as a composite partner for capping sensitive sensors, this also relates above all to microfluidic applications for bioanalysis. However, the necessity results from this of structuring the various silicate glasses of differing compositions. Depending on the application, greatly varying structures are necessary in the glass: holes having a high aspect ratio or defined bevels for through contacting, trenches for channel and diaphragm production, or also special shapes for high-frequency components.
While both high-precision and also efficient plasma etching methods (high-speed etching) exist for silicon structuring, the structuring of glass in large etching depths (greater than 10 μm) using plasma technology has only been possible very poorly in comparison up to this point. Thus, for example, until now technologies based on lasers, ultrasound, sandblasting, wet etching processes, or also sawing have still been preferred. Plasma etching methods have only allowed practical etching rates significantly less than 1 μm/minute until now. (X. H. Li, T. Abe, and M. Esashi, “Deep reactive ion etching of Pyrex glass,” in Proc. 13th IEEE MEMS 2000 Technical Digest, volume 1/23-27/00, Miyazaki, Japan, 2000, pages 271-276; J. H. Park et al., “Deep dry etching of borosilicate glass using SF6/Ar . . . ”, Microelectronic Engineering 82 (2005) 119-128) and a very restricted controllability of the etching profile. Thus, flattening of angles of slope (for example, to approximately 70°) has only been achieved using specially tailored mask geometry. Complex mask technology is also necessary in the existing processes. Thus, reaching etching gaps of 50 μm, for example, requires a stable nickel mask of 4 μm, (X. H. Li, T. Abe, and M. Esashi, “Deep reactive ion etching of Pyrex glass using SF6 plasma,” Sensors and Actuators A 87 (2001) 139-145) or 9 μm (J. H. Park et al., “Deep dry etching of borosilicate glass using SF6/Ar . . . ”, Microelectronic Engineering 82 (2005) 119-128). The production of such nickel masks using electrochemical methods is connected to additional outlay, because special intermediate layers are necessary for this purpose, which must also be structured. In addition, it is known from the above-mentioned publication that nickel results in a significant increase in mechanical stress.
Possibilities for increasing the etching rate have only been seen up to this point (X. H. Li, T. Abe, and M. Esashi, “Deep reactive ion etching of Pyrex glass using SF6 plasma,” Sensors and Actuators A 87 (2001) 139-145) by the use of a high ion acceleration voltage (proportional to the so-called electrical bias voltage) and a low operating pressure. The ion bombardment increased by the two parameters acts to increase the etching rate especially because the typically used glasses normally also contain Al2O3 and Na2O components, which do not form volatile reaction products in connection with the fluorine-based plasmas used. A slight increase of the etching rate is observed with the temperature (however, the temperature is negligible according to the statements of the authors) at 0.8 Pa, but its maximum still lies below the etching rate at low pressure (0.2 Pa). Therefore, according to the statements of the authors, the physically determined sputter etching clearly dominates. This is also the basis for all other known processes for plasma etching of glass substrates.
In U.S. Pat. No. 6,120,661 an apparatus is described for treating glass substrates by etching, CVC or sputtering. The processing conditions are not listed in detail and no structure forming treatment is disclosed.
In JP 2000 164567 A a plasma etching process is described in which only a mask of e.g. silicon oxide is utilized and which is used for etching a ferromagnetic thin film. It is a general prerequisite of an etching process that the mask material may not be attacked. The formation of structured components of silicon oxide cannot be derived from this publication.
U.S. Pat. No. 5,753,566 discloses a process and an apparatus, with which a glass layer is etched at slightly elevated temperature (70-110° C.). However, this document is not concerned with the formation of a structure on a component, but instead with etching away the complete surface (etch back) of a spin-on glass layer. This procedure is not in any event suitable for forming a structure on a component, i.e., for partial removal of a material composed of silicon oxide, especially of silicate glass, glass ceramic or quartz.